1. Field of the Invention
The present invention relates to a conductor pattern and an electronic component including the conductor pattern.
2. Description of the Related Art
In a conventional conductor pattern for an inductor formed by printing conductive paste, a pattern with a small width cannot be obtained and is not suitable for an inductor having a small deviation. When manufacturing the inductor with a small deviation, a conductive thin film is formed by sputtering, a conductor pattern for an inductor is formed by the combination of photo-lithography and etching. Then, the film thickness is further increased by plating so as to form a conductor pattern for an inductor having a small deviation and a large Q value. The plating process has a problem, however, of a long throughput time and a greatly increased cost.
Recently, a method using photosensitive conductive paste has been proposed for forming a conductor pattern. In this method, photosensitive conductive paste is coated and a conductor pattern is formed thereon by exposing, developing, and burning it.
When a pattern width and space of the conductor pattern for forming an inductor are reduced and further when an aspect ratio is increased by an increase of the conductor thickness in order to obtain the required Q value and a DC resistance, a deficiency occurs in that a spiral corner of the conductor pattern for the inductor is peeled and raised off a substrate during burning. This occurs because of the cross-sectional shape and stress of contraction during the burning required when using photosensitive conductive paste.
That is, a light beam such as a UV beam is attenuated gradually in the photosensitive conductive paste, so that a bottom portion of the photosensitive conductive paste is difficult to be exposed. A photo-cured area is therefore reduced gradually toward a lower portion, and as shown in FIG. 14, a cross-sectional shape of a conductor pattern 31 after development is generally liable to be an inverted trapezoid. A contraction rate of the conductor pattern 31 after burning is approximately 70% and a contact area between a substrate 30 and the conductor pattern 31 is further reduced. Therefore, the contact area between the substrate 30 and the conductor pattern 31 is comparatively small and a joining strength between the substrate 30 and the conductor pattern 31 is also comparatively small.
On the other hand, for a conductor pattern 32 for the inductor having straight lines 32a and corners 32b shown in FIG. 15, a large contraction stress K1 is produced on the lines 32a during burning. On the corners 32b, a large tensile stress K2 is produced in the width direction of the pattern due to the contraction stress K1 of the straight line 32a, so that the corner 32b is likely to be peeled and raised off the substrate 30 (see the conductor pattern 31 on the right side of FIG. 14).
In order to solve the problems described above, preferred embodiments of the present invention provide a conductor pattern that prevents corners from peeling and raising off a substrate, and an electronic component including such an improved conductor pattern.
According to a preferred embodiment of the present invention, a conductor pattern according to the present invention is formed from photo-sensitive conductive paste coated on a surface of a substrate by exposing, developing, and burning the photo-sensitive conductive paste, and the conductor pattern includes straight lines and corners connected to the straight lines, wherein the bottom surface cross-sectional width of the conductor pattern is not larger than the top surface cross-sectional width thereof, and wherein the bottom surface cross-sectional width of each of the corners is larger than the bottom surface cross-sectional width of each of the straight lines.
More specifically, the bottom surface cross-sectional width of each of the corners may preferably be at least about 1.07 times, more preferably at least about 1.5 times, that of the conductor thickness of each of the corners. Furthermore, the bottom surface cross-sectional width of each of the straight lines may preferably be at least about 0.67 times that of the conductor thickness of each of the straight lines.
With the unique construction and structure described above, the bottom surface cross-sectional width of the corner is larger than the bottom surface cross-sectional width of the straight line, so that the contact area between the corner and a substrate is increased compared with conventional conductor pattern. Thereby, the problems with conventional conductor patterns are solved.
An electronic component according to another preferred embodiment of the present invention includes a conductor pattern formed from photo-sensitive conductive paste coated on a surface of a substrate by exposing, developing, and burning the photo-sensitive conductive paste, and the conductor pattern includes straight lines and corners connected to the straight lines, wherein the conductor pattern is any one of conductor patterns having the features described above with respect to the first preferred embodiment of the present invention.